Orientation Of Microcrystals Research Articles

Link between plasma properties with morphological, structural and mechanical properties of thin Ti films deposited by high power impulse magnetron sputtering

The main focus of this work is to correlate the basic plasma properties with morphological, structural and mechanical properties of thin films to bridge the gap between the energy source, the plasma and materials. For this purpose, the deposition and growth of thin titanium films deposited by high power impulse magnetron sputtering (HiPIMS) at various discharge power densities, from 0.17 kW/cm 2 to 3.5 kW/cm 2 were studied, both experimentally and by kinetic Monte Carlo simulation. Simulations of film growth were performed with a three-dimensional kinetic Monte Carlo code (NASCAM) with ion fraction and species energy determined experimentally by mass spectroscopy . Our approach, which is not purely empirically driven, intends to reveal some insights of the mechanisms underlying the synthesis process, which determine the intrinsic material properties. In order to link HiPIMS plasma parameters and Ti film properties, we used different techniques to analyse Ti films. TEM, X-ray diffraction and AFM were used to evaluate the structural and morphological properties of the films, and nano indention was used to evaluate their mechanical properties. We observed that the orientation of micro-crystals, which constitute the films, changes when the discharge power density increases. At the same time, we show that the films nano hardness changes non-monotonically with the increase of the discharge power density; it decreases first, then increases. The surface roughness behaviour is also non-monotonic; first increasing, then decreasing with the further increase of the discharge power density. 3D modelling helped to reveal that these non-monotonic evolutions are due to a transition between thermally-driven to ballistically-driven Ti atom mobility. • Evolution of the film properties with increase of discharge power density in HiPIMS deposition • Combined analysis of the film morphology by a range of experimental methods and simulations • A correlation between ion energy distribution functions and properties of the deposited Ti film is demonstrated. • The average energy per deposited atom is the driving force for the changes in morphology and structure of deposited films.

X-ray diffraction study on the orientation dynamics of biaxial microcrystals under static and rotating magnetic fields

The orientation of microcrystals of DyBa2Cu3Oy (y ~ 7) under static and rotating magnetic fields was studied.

X-ray diffraction from magnetically oriented microcrystal suspensions detected by a shutterless continuous rotation method

In this study, the magnetically oriented microcrystal suspension (MOMS) method is combined with the shutterless continuous rotation method. In the MOMS method, the suspension has to be rotated to maintain the three-dimensional orientation of microcrystals. This means that it is compatible with the continuous rotation method, which also utilizes sample rotation. The time constants of the two methods should match to allow their successful combination. The conditions required for the MOMS method for combination with the continuous rotation method are investigated. Experiments are performed with a complementary metal–oxide semiconductor (CMOS) detector and the restriction imposed on the time constant for the MOMS method by the continuous rotation method is examined. The combination of these two methods is a promising approach for realizing the structure analyses of biomolecules from their microcrystalline powders.

Single crystal elastic constants evaluated with surface acoustic waves generated and detected by lasers within polycrystalline steel samples

We report on a laser generated and detected surface acoustic wave method for evaluating the elastic constants of micro-crystals composing polycrystalline steel. The method is based on the measurement of surface wave velocities in many micro-crystals oriented randomly relative to both the wave propagation direction and the sample surface. The surface wave velocity distribution is obtained experimentally thanks to the scanning potentiality of the method and is then compared to the theoretical one. The inverse problem can then be solved, leading to the determination of three elastic constants of the cubic symmetry micro-crystals. Extensions of the method to the characterization of texture, preferential orientation of micro-crystals or welds could be foreseen.

Experimental verification of hypothesis of dd reaction enhancement by channeling of deuterons in titanium deuteride at ultralow energies

Energy dependence of the neutron yield from the d(d, n)3He reaction in a textured target of titanium deuteride with predominant [100] orientation of microcrystals is investigated. The measurements were performed for the incident deuteron energies ranging from 7 to 12keV in the laboratory coordinate system. It is shown that the energy dependence of the enhancement factor is described not only by the screening potential but also by simply taking account of channeling effects.

Effect of the crystal structure of a deuterated target on the yield of neutrons in the dd reaction at ultralow energies

The energy dependence of the neutron yield in the d(d, n)3 He reaction proceeding in a textured titanium deuteride target with the preferred orientation of microcrystals in the [100] direction has been studied. Measurements have been performed for the energy range of incident deuterons of 7–12 keV in the laboratory system. It has been shown that the energy dependence of the enhancement factor of the reaction is described not only by the screening potential but also by the simple inclusion of channeling effects.

Orientation of Diamagnetic Layered Transition Metal Oxide Particles in 1-Tesla Magnetic Fields

The magnetic field-driven orientation of microcrystals of six diamagnetic layered transition metal oxides (HLaNb(2)O(7), HCa(2)Nb(3)O(10)·0.5H(2)O, KNaCa(2)Nb(4)O(13), KTiTaO(5), KTiNbO(5), and H(2.2)K(1.8)Nb(6)O(17)·nH(2)O) suspended in epoxy resins was studied by X-ray diffraction using permanent magnets producing a 0.8 T field. Although the degree of orientation, quantified as the Hermans order parameter, was strongly affected by the particle size distribution, in all cases microcrystals with ∼1-2 μm lateral dimensions were found to orient with the magnetic field vector in the layer plane. Control of the orientation of ionically conducting layered oxides is of interest for practical applications in batteries and fuel cells. The consistent direction of orientation of the lamellar oxides studied can be rationalized in the framework of a quantitative bond anisotropy model developed by Uyeda (Phys. Chem. Miner.1993, 20, 77-80). The asymmetry of metal-oxygen bonding at the faces of the octahedral layers results in long and short M-O bonds perpendicular to the plane of the sheets. This distortion of the M-O octahedra, which is a structural feature of almost all layered materials that contain octahedral bonding frameworks, gives rise to the diamagnetic anisotropy and results in an easy axis or plane of magnetization in the plane of the sheets.

Structure of framboidal pyrite: An electron backscatter diffraction study

The detailed crystallography of natural pyrite framboids has been determined for the first time using electron backscatter diffraction techniques. The crystallographic ordering of microcrystals correlates positively with morphological ordering; the crystallographic orientations are random in morphologically disordered framboids and are almost ordered in morphologically ordered framboids. Morphologically ordered framboids involve two types of systematic misorientations across the microcrystal boundaries: low-angle (ca. <20°) and high-angle (ca. 70.90°) misorientations. The low-angle misorientation probably reflects slight physical misalignment of microcrystals in the packing structure, whereas the high-angle misorientation is considered to result from the dichotomy of the pyrite microcrystals having fourfold morphological symmetry but only twofold crystallographic symmetry about <100>. Thus, the crystallographic orientation of microcrystals is not uniform, even in highly ordered framboids. This suggests that the self-organization of microcrystals in pyrite framboids is not crystallographically controlled, for example by sequential replication of existing microcrystals, since this would not result in high lattice misorientation angles between adjacent microcrystals. Presumably, the self-organization process is a consequence of the aggregation of multiple equidimensional and equimorphic microcrystals that have nucleated in a fixed volume. We suggest that the regular arrangement of microcrystals occurs by the physical rotation (reorientation) of individual microcrystals, driven by the reduction in surface free energy between neighbors.

Influence of alloy composition and local environment on the magneto-optical properties ofCoxPd1−xalloys

Results of ab initio calculations performed to investigate the dependence of magneto-optical properties of ${\mathrm{Co}}_{x}{\mathrm{Pd}}_{1\ensuremath{-}x}$ alloys on chemical ordering and alloy composition are presented. A procedure of averaging the calculated spectra for compounds with respect to the orientation dependence of the gyration vector is proposed that makes it possible to account for the effects of random orientation of microcrystals in polycrystalline samples. Good agreement between theoretical and experimental spectra for varying alloy composition is found demonstrating the applicability of the theoretical approach.

Observation on Skin-Core, Microfibril and Pleated Band Morphology in Poly(p-phenylene Terephthalamide) Fibers Using Transmission and Scanning Electron Microscopes.

Poly (p-phenylene terephthalamide) fibers (Kevlar 29 and 49) were thin-sectioned or treated with a mixed solvent of sulfuric-acid/water (SAW) to be observed in transmission and/or scanning electron microscopes. Microfibrillar and pleated-band morphology existed in Kevlar 29 and 49 fibers, while the skin-core structure was confirmed only in Kevlar 29 fiber. A microfibril ca. 100nm thick is composed of several tens of needle-shaped microcrystals 10_??_20nm thick, being pleated with a period of 500_??_600nm along the fiber axis. Hydrogen-bonding or crystal structure in the core region was considered to be more ordered than that in the skin region in the case of Kevlar 29 fiber. Orientation of microcrystals in each microfibril was incoherent although b-axis orientation mainly distributed around the radial direction. Such tendency is more prominent for Kevlar 29 fiber which was finally suggested to assume the hierarchical morphology of “pleated-microcrystal band”.

A study of the effect of the orientation of microcrystals on the properties of iron-based amorphous alloy Fe78Si9B13

A study of the effect of the orientation of microcrystals on the properties of iron-based amorphous alloy Fe₇₈Si₉B₁₃

The multibeam interaction effect on electron diffraction in polycrystals with a different degree of orientation of microcrystals

The multibeam interaction effect on electron diffraction in polycrystals with a different degree of orientation of microcrystals

Structure Change of Microcrystalline Silicon Films in Deposition Process

Structure change with thickness of films of microcrystalline silicon prepared by reactive sputtering and glow discharge techniques has been investigated with transmission electron microscopes and a Fourier transform infrared spectrophotometer. An amorphous state changes into a microcrystalline one with increase of the thickness from 10 to 100 nm. Sufficiently thick films (>0.4∼0.5 µm) deposited by the reactive sputtering show a columnar structure with an orientation of microcrystals {110} parallel to the substrate. As the orientation of the microcrystals develops with thickness, IR absorption bands due to Si–H stretching become sharper.

Bombardment-induced corrosion resistance of aluminum

Ion bombardment of aluminum films at doses greater than 3×1014 cm−2 inhibits the etching of aluminum by acids. Ions of B, P, N, Si, Al, As, and Ar are effective inhibitors. Bombardment randomizes the orientation of microcrystals; however, this may not be the primary reason for the observed corrosion resistance.

Orientation of microcrystals for X-ray diffraction studies

A method is described for obtaining X-ray diffraction photographs, equivalent to those obtained under single-crystal rotation conditions, from materials available only in the form of fine microcrystalline powders of acicular or platy habit. The technique involves dispersing the crystalline powder in an appropriate thermoplastic polymer followed by streaming orientation of the particles in an extrusion process. The particles are held in their new positions by solidification of the polymer melt. With acicular powders, and using a polyethylene matrix, the orientation is improved by cold drawing. The oriented composite is immediately ready for X-ray studies.